1. Field of the Invention
The present invention relates to a method for preventing fouling of an exhaust gas flow path of a burning equipment and to a method for removing ammonium hydrogen sulfate which is contained in an exhaust gas of the burning equipment.
2. Description of the Related Art
In the burning equipment including a boiler which uses a sulfur-containing substance as a fuel such as a heavy oil, a coal, a natural gas, a biomass, and a wasted substance, an SO2 gas is generated when these fuels are burnt.
This SO2 gas is partially oxidized to SO3 by those substances including O2 in the exhaust gas, oxidation catalyst components contained in the fuels (V2O5, etc.), and the oxidation catalyst (V2O5) and the like contained in the denitration catalyst. This SO3 becomes sulfuric acid by taking water which is present in the exhaust gas during the time when the temperature of the exhaust gas descends.
On the other hand, in the burning equipment including a boiler, NH3 is charged for denitration in the denitration equipment (hereinafter, sometimes referred to as “SCR”) and for neutralization of the SO3 mist in the electrical dust collector (hereinafter, sometimes referred to as “EP”).
During this process, if the amount of NH3 is two times or more in the molar ratio relative to SO3, ammonium sulfate is generated: while if the amount thereof is less than two times, ammonium hydrogen sulfate is generated. Therefore, when amount of SO3 generated is increased due to change of the fuel quality, deterioration of member equipment to constitute the boiler, and so forth, the molar ratio of NH3/SO3 decreases relatively thereby causing increase of the production ratio of ammonium hydrogen sulfate.
It is known that the ammonium hydrogen sulfate which is generated in the burning equipment is deposited and adhered in the economizer (hereinafter, sometimes referred to as “ECO”) that is installed at the boiler outlet port, in the heat-exchanging member including an element of the air-heating unit (hereinafter, sometimes referred to as “APH”), and in SCR, EP, and the like, thereby causing problems such as corrosion and clogging of the smoke path. To overcome these problems due to ammonium hydrogen sulfate, following means have been proposed.
In the patent document 1, a proposal was made as to the method for preventing fouling that is caused by ammonium hydrogen sulfate and so on, wherein a quaternary ammonium compound is contacted with the exhaust gas which contains ammonium hydrogen sulfate and so on thereby changing ammonium hydrogen sulfate and so on to different substances, which are then liquefied or vaporized.
In the patent document 2 and the patent document 3, proposals were made as to the method for reducing the SO3 compound (ammonium hydrogen sulfate), wherein a Mg compound is introduced into the exhaust gas so as to deactivate heavy metal compounds including V2O5 which are catalysts to generate the SO3 compound, or a Fe compound is included in the fuel in order to facilitate the burning of the unburnt carbons whereby bringing the exhaust gas to the low-oxygen state so that the production amount of SO3 may be suppressed.